Compact disks (CD) and video disks (LD) as information recording media are often available in the form of disk cartridges having the disks accommodated in casings whereupon recording/reproducing machines such as disk players are loaded with the cartridges. The disk players have a drive shaft for driving the disk and a pickup for recording and reproducing bits of information into and from the disk.
To protect these disks against deposition of dust and debris, damages during handling, and temperature influence, the disks are conventionally enclosed in casings. Each casing includes a center aperture located generally at the center of the casing for allowing the drive shaft to extend therethrough to engage the disk annular hub for driving and an access window located radially outward of the center aperture for allowing a pickup to make access to the disk therethrough for recording and reproducing when the disk player is loaded with the cartridge. The casing further includes movable shutters for normally closing the windows when the disk is not used.
For recording or reproducing numerous data for an instant in an optical disk or the like, a plurality of pickups are required and the casing must then be provided with a plurality of access windows through which the pickups can make access to the disk. The shutters are thus required to simultaneously open or close the center and access windows during loaded and unloaded periods of the disk for the purpose of protecting the disk against dust and debris. Various types of shutters have been proposed for simultaneously opening and closing these windows. A simple one is a unidirectional slide shutter, which would result in a disk cartridge of increased size as a whole. A combination shutter including a shutter member for a center aperture and a rotary shutter member having a large diameter is useful. In order for a single slide to actuate both the shutter members, the slide must be moved over a large stroke and thus needs a relatively large size of mechanism for driving the slide as opposed to the general requirement for a smaller size of actuation mechanism. An additional problem arises with a spring for biasing the slide in closing or opening direction. As the stroke of the slide increases, the difference in spring force between the open and closed states becomes larger. In either of the states excess loads can be applied to the related members, which would experience distortion during storage particularly at elevated temperatures. In some cases, a great force is required for the actuation mechanism to open the shutter.